1. Field of the Invention
The present invention is generally related to snorkels used by skin divers and swimmers. More particularly, this invention is concerned with preventing water from entering and flooding a snorkel.
2. Description of the Prior Art
Skin divers and swimmers use the snorkel as a means to breathe while swimming face down on the water surface. The snorkel functions as a conduit between the diver""s mouth and the overhead air. Typically, the open end of the snorkel conduit extends a short distance above the water surface. Occasionally, due to swimming movements or wave action, small amounts of water flow or splash into the open end of the snorkel and partially floods the conduit. An experienced skin diver can sense when water enters the snorkel and responds by immediately stopping inhalation. Respiration is resumed after the snorkel has been purged of water. Inexperienced skin divers find occasional flooding especially troublesome because, undetected, water can be inhaled resulting in coughing and extreme discomfort.
Water will also flood the snorkel when the swimmer deliberately dives below the water surface. The snorkel conduit will be completely flooded with water when the swimmer returns to the surface. When the open end of the snorkel is again above the water surface, the flooded conduit is purged for respiration by exhaling an explosive blast of air into the mouthpiece.
Surface tension forms the purging blast of air into a bubble that spans the cross section of the snorkel conduit. Pressure within the bubble expands the bubble toward the open end of the conduit. As the leading surface of the bubble moves away from the mouthpiece, the bulk of the water within the conduit is pushed ahead of the bubble and out the open end.
The purging bubble of air will slip past water that adheres to the inside surface of the conduit. After the purging air bubble is spent, residual water will flow down the inside surface toward the mouthpiece. Also, water which splashes into the open end of the snorkel conduit due to swimming movements or wave action will typically strike and adhere to the inside surface of the conduit and thereafter flow toward the mouthpiece. Water accumulates at the lowermost portion of the snorkel conduit, typically adjacent the mouthpiece, and can soon obstruct the conduit. Unless the conduit is completely blocked, a slow and cautious inhalation is possible after which another purging exhalation can be made.
The respiratory effort needed to purge a snorkel is significant. Many skin divers and swimmers lack the respiratory strength needed to completely purge a flooded snorkel with a single exhalation, and must repeat the purging procedure several times. Also, water will sometimes enter the snorkel just as the swimmer has completed an exhalation, leaving very little air in the lungs to satisfactorily complete a purge.
As a consequence of the difficulties typically encountered by a skin diver or swimmer when trying to purge a flooded snorkel, a number of inventions have been proposed to protect the snorkel opening with devices that prevent water from entering the conduit, even when the swimmer dives underwater.
U.S. Pat. No. 2,317,236 entitled Breathing Apparatus for Swimmers issued to C. H. Wilen, et al, on Apr. 20, 1943, teaches an inverted opening with a caged buoyant ball arranged to block the above water end of the snorkel whenever water starts to enter. Such inverted ball valves are bulky, tend to snag, often fail to seal completely and, also, significantly increase respiratory effort. Although once popular, such devices are now considered unreliable and obsolete.
U.S. Pat. No. 4,071,024 entitled Snorkel, issued to Max A. Blanc on Jan. 31, 1978, teaches an air-entrapping cap which is mounted on the above water opening of the snorkel. A tortuous passage in the cap retards water flow into the snorkel. Although such a cap is somewhat effective in blocking the occasional splash of surface water into the snorkel, it also retards expulsion of water that enters the snorkel during a dive below the water surface. The significant increase in respiratory and purging effort limits its utility and subsequent popularity.
U.S. Pat. No. 4,805,610 entitled Swimmer""s Snorkel, issued to Howard Hunt on Feb. 21, 1989, teaches a buoyant cap attached to an internal non-buoyant ball valve which is arranged to block the snorkel opening whenever water covers the cap. As with the valve of Wilen, the Hunt valve is bulky, tends to snag, and does not reliably prevent water from entering the snorkel.
U.S. Pat. No. 5,117,817 entitled Vertical Co-Axial Multi-Tubular Diving Snorkel, issued to Hsin-Nan Lin on Jun. 2, 1992 teaches an annular float arrangement which blocks the above water end of the snorkel whenever water start to enter. To assist in purging, the Lin snorkel also teaches a secondary purge tube within the breathing conduit. The Hsin-Nan Lin snorkel is an improvement over Wilen. However, the valve arrangement of the Hsin-Nan Lin snorkel significantly increases respiratory effort, and if water somehow gets into the snorkel, for example through the mouthpiece, that water is difficult to expel.
Somewhat similar to Blanc, U.S. Pat. No. 5,199,422 entitled Modular Snorkel, issued to Stan Rasocha on Apr. 6, 1993, teaches an exhaust valve mounted on a cap that covers the upper end of the snorkel. The cap restricts the entry of splashed water into the snorkel. The exhaust valve on the cap permits the direct expulsion of water from within the snorkel during a purging exhalation. Although Rasocha""s snorkel on an improvement over Blanc, it nevertheless permits water to flood the snorkel when the swimmer dives below the surface.
In view of the foregoing factors, conditions and problems which are characteristic of the prior art, the instant invention was conceived. It is the object of the instant invention to provide a shield that reliably prevents water from entering the open end of a snorkel, but never blocks exhalation flow, does not increase respiratory effort and does not affect the ability of the swimmer to purge the snorkel of water or saliva.
The instant invention is a skin diving snorkel having a conduit with an end above the water surface, and an underwater end that terminates in a mouthpiece. The mouthpiece provides a flow path between the conduit and the interior of the diver""s mouth. A buoyant chamber, separate from the conduit, surrounds and is coaxial with the conduit above water end. A lower opening in the chamber is joined to the conduit by a convoluted diaphragm. The convoluted diaphragm provides a flexible and watertight barrier that enables the chamber to be easily buoyed a short distance upward, guided by the snorkel conduit. The conduit""s open end protrudes loosely through an upper opening in the chamber. The conduit open end carries a flexible circular diaphragm which, when it makes contact with the upper opening of the buoyed chamber, serves as a check valve allowing exhalation flow from the conduit to ambient, but blocks the flow of water into the snorkel. In addition, an optional purge valve adjacent the conduit underwater end also allows flow from the conduit to ambient, but not in the reverse direction.